The object of the present invention is a method for conditioning electronic microcircuits in modules, each of which microcircuits is designed to receive an integrated circuit, generally called a chip, and thus forming electronic microcircuit modules. A further object of this invention is the electronic microcircuit modules thus obtained. Indeed, with the increase in production volumes of chip cards equipped with such modules, chip cards which are used more and more frequently in daily life, the processes for manufacturing these modules have been modified to meet a demand for quantity, occasionally to the detriment of the quality and reliability of the products obtained. The invention further relates to the installation of these modules in chip cards or other substrates.
Chip cards are obtained by arranging an electronic microcircuit module in a recess formed in the thickness of the card. This electronic module includes a microcircuit that presents an upper contact face having conductive areas, on one side of a visible face of the card. The other face of the electronic module bears a chip, which is then hidden in the recess of the card. The chip is secured and connected on a side opposite the upper face to a lower face of conductive areas.
With regard to the prior art, French patent no. FR-A-2 488 446 describes a compact electronic module designed to be mounted in an identification card. The module includes a chip glued by its base to a first face of a metallic plate including contact zones. The chip is connected to these contact zones by conductor wires that connect an upper part of the chip to these contact zones. The module includes a support element or substrate against which the metallic plate may be supported. The support element then includes one or more windows to allow the chip to be glued and/or connected to the metallic plate.
The gluing of the chip presents a problem, because it is not reliable in the longer term. Moreover, it requires that spots of glue be dispensed in uniform quantities and at closely defined intervals. But the presence of bubbles in the gluing plane can weaken the mechanical strength of the module obtained. In fact, in order to meet the requisite production conditions, glue is used that is capable of bonding quickly at relatively high temperatures. But these glues also cause the formation of bubbles and are therefore responsible for the instability of the chip mounting on the metallic plate.
In order to lend mechanical strength to the module, and at the same time to protect the conductor wires and the chip, a coating product is used to coat them. The coating product may be a resin, for example. This stiffens and is polymerised under the effect of heat treatment or irradiation with infrared or ultraviolet light. These coating resins present a problem in themselves. Their wettability is unstable, and depends in part on external conditions that cannot be controlled without significant expenditure. The resin deposited forms a dome of the side of the lower face, but it spreads when it is deposited because it is not yet polymerised. This spreading of the resin drop causes the mechanical strength of the module to be weakened and provides poor protection of the microchip and its conductor wires.
The flow of this drop creates difficulties because it also makes the module too wide. For the positioning of this drop it is therefore necessary to provide a periphery around the drop, in order to preserve peripheral zones for attaching the module to the card. These attachment zones are then glued to a shoulder provided in a lateral rabbet of the chip card recess.
On the other hand, a warm polymerisation resin which polymerises under the effect of ultraviolet light irradiation provides correct results in terms of wettability, thereby providing sound protection for the item it coats. But this resin does not lend sufficient mechanical strength to the module. Moreover, ultraviolet irradiation can disrupt the memory zones of the chips present on these modules.
To address this problem, solutions are known using resins that exhibit good mechanical strength qualities, and that allow the drop diameter of such a resin to be reduced. These solutions implement a barrier to retain the outflow of the drop. The barrier may be obtained for example by silk-screen printing of a silicone ring deposited on the periphery of the zone of the metallic plate that is to receive the chip. However, the efficiency of this solution is limited, and moreover it does not perfectly limit the flow of the drop if the plane is slightly inclined.
Otherwise, U.S. Pat. No. 5,989,941 describes the use of a barrier to channel the coating product and permit an improvement of the heat dissipation and the mechanical adhesion of an electronic module. Solutions incorporating such a barrier are also known by the technical name “dam & fill”. The barrier is fixed on a support of the module by an adhesive layer. It is fixed in position on one side of the same support that retains the contact plate to which the chip is connected. This barrier corresponds to a film including a window having a dimension such that the contact plate forming a model of metallised circuit and the chip are both framed entirely inside this window. According to this document only the use of film including at least one conductive membrane is known. Moreover, this film is mounted on the module only after the metallic circuit has been created, and after the chip has been connected to this circuit.
The film includes for example a long strip, one of the faces of which is coated with adhesive material with an applicator. According to this document, the film is then cut to size, so that windows are formed thereby. The film windows are arranged so that they cooperate with different zones of a support, each zone including a metallic circuit and a chip connected with its circuit, the support always including tabs that enable it to be affixed to the chip card. The film is glued on the support in such manner that each window is arranged around only one circuit. Because of the thickness of the film, the window then enables the outflow of coating material to be limited when the drop of resin is deposited on the circuit with its chip.
In order to be mounted then in an identification card, the electronic module obtained according to this instruction must be coated with a specific glue that enables it to adhere to the bottom of an identification card recess, due to the very nature of the type of film used.
The difficulty with micromodules according to the state of the art consists in the fact that, even when they are furnished with a film preventing the outflow of the resin drop, they require long, painstaking and inefficient preparation stage, which corresponds to the stage of mounting the micromodule on the card. In fact, in order to mount the micromodule on the card, a second film is used, which is coated with “hot-melt” glue and has been pre-cut in a first stage to form windows therein. Then, this glue film is hot rolled onto the micromodule, and lastly in a third stage the glue of this film is activated for a final mounting of the micromodule on the card.
The first stage is inefficient because the cutting shears adhere to the glue film even after it has cooled, and prevent faster manipulation relative to the film. This first stage is therefore incompatible with the speed required for mass production of chip cards. Moreover, in order to guarantee correct positioning of the glue film on the micromodule it is necessary to provide for bead removal of one with respect to the other, which makes for a slow procedure. With a fast procedure, when the glue film lamination takes place, there is a significant rejection rate. Rejection at this stage is very expensive, since none of the rejected components can be re-used.
The use of such a glue film is necessary to achieve a production speed that is faster than processes in which each micromodule is glued individually. But the use of such a glue film is obligatory in order to be able to affix the micromodule to the bottom of its recess, even though its reliability over time is limited.
The task of the present invention is to remedy the problems described in the aforegoing by redefining the conditioning of the electronic microcircuit, in order to facilitate the subsequent card mounting of the module including this microcircuit. In this way, the efficiency of the electronic module conditioning stage is improved, and furthermore the long term reliability of the mounting of such an electronic module on a card is increased. The reliability of the finished product is increased because the reliability of the gluing of the module on the card is improved, and also because the reliability of the gluing of the chip to the back of the electronic microcircuit is improved. Effectively, the invention provides for transferring all the gluing means to the electronic microcircuit module.